I have just read a most exciting tip in the latest edition of ‘The Cottage Gardener’, the quarterly magazine of The Cottage Garden Society and I thought I would pass it on.
I am indebted to Jo Webber from Looe, Cornwall, who wrote about her successful experiment of increasing her stock of Verbena bonariensis by layering, a propagation technique more commonly used with shrubs such as forsythia, daphne, viburnum, rhododendrons, azaleas and camellias. Jo explained that in October, when the plants had finished flowering, she cut off the seedheads and gently bent the tall stems to the ground, covering them with soil at each leaf node. Apart from making sure they did not dry out, Jo then ignored them until April when she was delighted to find lots of new plants! They were separated from the main stem and replanted where she wanted them.
A very unusual way of propagating an herbaceous perennial but I suppose it makes sense that in Spring, the growth hormones will be strongest in the leaf axils where side shoots would naturally form. Jo doesn’t say whether she wounded the stem at each leaf node before burying them, something you would normally do with shrubs, but maybe that is not required in this case.
I think this is an amazing and innovative idea and something I am definitely going to try for myself. I already have quite a few plants of this variety but I would happily have more. Normally, the stems would die back and new shoots would appear from the base each year but I have noticed that in mild winters, this species often shoots again from the previous years growth although a late frost can cut it down.